A variety of methods for imparting flame retardance to polyester-based fiber products by post-processing have been hitherto known. For example, there is known a method of attaching, to polyester-based fiber products, a flame-retardant processing agent which is prepared by dispersing, with a dispersant in water, a halogen-containing compound, typically a brominated cycloalkane such as 1,2,5,6,9,10-hexabromocyclododecane as flame retardant (see, for example, Japanese Examined Patent Publication No. 53-8840 (1978)). However, by the method of imparting flame retardance to polyester-based fiber products by attaching halogen-containing compounds thereto will cause some problems: when such polyester-based fiber products burn, harmful halogenated gas is formed and this will exert harmful influence to the environment. Therefore, in recent years, use of such halogen-containing compounds as flame retardant has been restricted.
Under such circumstances, there have been made attempts to impart flame retardance to polyester-based fiber products by use of halogen-free phosphoric ester as flame retardant instead of those halogen-containing compounds. As such phosphoric esters, for example, aromatic monophosphates such as tricresyl phosphate and aromatic diphosphates such as resorcinol bis(diphenyl phosphate) are known. However, such phosphoric esters that have hitherto been known as flame retardant can impart polyester-based fiber products washing-resistant flame retardance, but are not sufficient in resistance to dry cleaning.
Moreover, even if a polyester-based fiber product is provided with flame retardance by using such a phosphoric ester, the phosphoric ester gradually moves to the surface of the polyester-based fiber product with time. During the movement, a dispersion dye and the like used for the dyeing of the polyester-based fiber product also move together with the phosphoric ester to the surface while being dissolved in the phosphoric ester to cause so-called “surface bleeding”. Therefore, there arises a problem of reduction in color fastness.
The present inventors made study to solve the above-mentioned problems in the conventional flame-retardant processing of polyester-based fiber products. As a result, they found that use of some kind of phosphoric acid amide as flame retardant made it possible to impart durable flame retardance to polyester-based fiber products without using halogen-containing flame retardant.
Thus, the present inventors have reached the present invention. It is therefore an object of the present invention to provide a flame-retardant processing agent capable of imparting durable flame retardance to polyester-based fiber products, a flame-retardant processing method using the same, and to flame-retardant processed polyester-based fiber products obtained using the same.